1Department of Physics, Mesoscopic and Multilayers Structures Laboratory, Faculty of Science, University of Dschang, P.O.Box: 479 Dschang, Cameroon.2Department of Physics, Laboratory of Electronics and Signal Processing, Faculty of Science, University of Dschang, P.O.Box 67, Dschang, Cameroon.3Department of Physics Laboratory of Mechanics and Modeling of Physical Systems, Faculty of Science, University of Dschang, P.O.Box 67 Dschang, Cameroon.